A.4 SCS Curve Numbers
| Land Use Description | Hydrologic Soil Group | |||
| A | B | C | D | |
| Cultivated land Without conservation treatment With conservation treatment | 72 62 | 81 71 | 88 78 | 91 81 |
| Pasture or range land Poor condition Good condition | 68 39 | 79 61 | 86 74 | 89 90 |
| Meadow Good condition | 30 | 58 | 71 | 78 |
| Wood or forest land Thin stand, poor cover, no mulch Good cover | 45 25 | 66 55 | 70 77 | 83 77 |
| Open spaces, lawns, parks, golf courses, cemeteries, etc. Good condition: grass cover on 75% or more of the area Fair condition: grass cover on 50-75% of the area | 39 49 | 61 69 | 74 79 | 80 84 |
| Commercial and business areas (85% impervious) | 89 | 92 | 94 | 95 |
| Industrial districts (72% impervious) | 81 | 88 | 91 | 93 |
| Residential Average lot size (% Impervious) 1/8 ac or less (65) 1/4 ac (38) 1/3 ac (30) 1/2 ac (25) 1 ac (20) | 77 61 57 54 51 | 85 75 72 70 68 | 90 83 81 80 79 | 92 87 86 85 84 |
| Paved parking lots, roofs, driveways, etc. | 98 | 98 | 98 | 98 |
| Streets and roads Paved with curbs and storm sewers Gravel Dirt | 98 76 72 | 98 85 82 | 98 89 87 | 98 91 89 |
- Antecedent moisture condition II; Source: SCS Urban Hydrology for Small Watersheds, 2nd Ed., (TR-55), June 1986.
- A good cover is protected from grazing and litter and brush covers soil.
- Curve numbers are computed assuming that the runoff from the house and driveway is directed toward the street with a minimum of roof water directed to lawns where additional infiltration could occur.
- The remaining pervious areas (lawn) are considered to be in good pasture condition for these curve numbers.
- In some warmer climates of the country, a curve number of 95 may be used.